There's big news for fans of the Forza franchise, as Porsche, one of the most …

I've been really impressed with the way that Forza Motorsport 4 developers Turn 10 have managed to keep player interest in the game roughly four months after the game's release. The steady stream of DLC has been arriving at the rate of 10 cars a month, and the sixth installment, the Pirelli Car Pack, hits the Xbox Live Marketplace today. I spoke with lead developer Dan Greenawalt about today's DLC and title update, as well as the upcoming return of Porsche cars to the series and the recently announced Forza Horizon spin-off.

Greenawalt said he's been impressed by the extent the Forza community has embraced the series' latest iteration. He chalks up some of the game's longevity to the steady stream of DLC, as well as the monthly rivals challenges, but said he's still been surprised at the way players have repeatedly come back to the game after the release of big titles like Skyrim.

While the team at Turn 10 expected that the most devoted players would start maxing out at level 150 after about nine months; Greenawalt said they've seen people getting there in just four! As a result, today's title update increases the level cap to a scarcely believable 999, which will likely keep those obsessive players busy for a little while longer.

The coming return of Porsche

When I reviewed Forza Motorsport 4 in October, I pointed to the absence of Porsche as one of the game's few downsides. Turn 10 had been unable to negotiate the rights to Porche's cars with Electronic Arts, which has an exclusive license to use the Stuttgart company's products in video games. Greenawalt told me that negotiations between Turn 10 and EA had never actually ended though, and several months ago Turn 10, EA, and Porsche were able to reach a deal that all parties were happy with.

An end to sleepless nights for the lawyers meant more sleepless nights for the developers, as another 30 new Porsche models have to be added to their already full pipeline. As a result, we'll have to wait until May 22 for the Porsche expansion pack, which will include seven cars that are completely new to the series. The expansion pack also adds 20 new events to the World Tour and 10 new achievements, something the game's flexible architecture has made possible. The expansion pack will set you back a hefty 1600 MS points ($20), but then again it does add another five hours of new challenges.

Forza Horizon

Greenawalt was relatively guarded with details about Forza Horizon, a newly announced title in the series that's set to debut this fall. Forza Horizon is a partnership with Playground Games, a 'supergroup' of UK game developers who've previously been responsible for racing titles like PGR, DiRT, and Blur.

Greenawalt said the game has been designed with a different vision in mind compared to Forza Motorsport 4 (and FM5, due to arrive next year), but both Turn 10 and Playground share the same desire to turn gamers into the next generation of car lovers (and vice versa). The new game will make use of bits of Forza Motorsport 4's physics engine, Greenawalt said, telling me that the active collaboration between Turn 10 and Playground will effectively give players the benefit of not one but two teams of developers.

We'll bring you more news about Forza Horizon as and when we find out. In the meantime, the March Pirelli DLC pack (560 MS points, $7) should be available for download today.